Specifically, it is one of four components that form lipid nanoparticles (LNPs), which encapsulate and protect the otherwise fragile mRNA that is the active ingredient in these drugs.

[1][2] These nanoparticles promote the uptake of therapeutically effective nucleic acids such as oligonucleotides or mRNA both in vitro and in vivo.

[3][4] Below physiological pH, ALC-0315 becomes protonated at the nitrogen atom, yielding an ammonium cation that is attracted to the messenger RNA (mRNA), which is anionic.

[7] Its chemical properties as a tertiary amine mean that its cation can form an ionic bond to the messenger RNA which carries the genetic information for the SARS-CoV-2 spike protein formation in the human body.

[2][8] In December 2021 there were objections raised against the use of ALC-0315 and ALC-0159 (and some other solid lipid nanoparticles) in humans by critics of mRNA-COVID-19 vaccines in Germany but the German pharmaceutical trade journal Pharmazeutische Zeitung (de) and the German investigative collective Correctiv refuted this and stated as one important reason that the European Medicines Agency has approved the vaccine and this includes all its ingredients.